The coal dealers assistant [electronic resource] : Being tables calculated for the ready and easy finding out the true value of any number of Chalderns, from 1 to 200, at any of the usual prices, from 15s. encreasing 3d. each to 1l. 10s. per chaldern without mettage, and may serve for any higher price, by following the directions in the table annexed. For the use of masters of ships and colliers trading coastways, from the ports of Newcastle, Sunderland, Blythe, &c. By a gentleman of Sunderland. Never before published.